Japanese Unexamined Patent Application Publication No. 2000-330798 discloses a technique of a controller for examining interrupt control on an interrupt signal from an input/output device to a processor. The interrupt controller in Japanese Unexamined Patent Application Publication No. 2000-330798 includes a register that keeps the history of the interrupt signal. After interrupt with the interrupt signal, the interrupt controller examines the interruption with reference to the contents of the register.